Method and apparatus for heavymedia separation



E. c. BlTzER 2,428,777 METHOD ANDv APPARATUS FOR HEAVY-MEDIA SEPARATION Filed- Aug. 16, 1943` 3 Sheets-Sheet l oct, 14, 1947.

EDMUND C. BITZER v INVENTOR.

a' ATTORNEY E. C; BITZER Oct. 14, 1947.

METHOD AND APPARATUS FOR HEAVY-MEDIA SEPARATION 3 Sheets-Sheet 2 Filed Aug. 16, 1943 r .ww n". E .mfc w m E ay fik/ 1. m diorney E. C. BITZER Oct, 14, 1947.

METHODl AND APPARATUS FOR HEAVY-MEDIA SEPARATION Filed Aug. 16, 1943 3 Sheets-Sheet 3 Fi'g.

EDMUND c. BITZER INVENTOR .BY

ATTORNEY :METHOD PATENT orricr.N

AND APPARATUS FOR HEAVY- MEDIA SEPARATION .v l. c Edmund C. Bitzer, Golden,

Colo., assignor. to i'.

Colorado Iron Works CompanmvDenver, Colo., a. corporation of Maine y Application August 16, i943, serial No. 49ans .by which such apparatus is adapted for heavymedia separations.

As a result of relatively recent developments, heavy-media separations have proven particularly eflicacious in the treatment of low grade ores and certain other types of materials which cannot be processed economically by older ore dressing methods. As an example, iron and manganiferous iron ores have been successfully treat'- ed by these methods, as have various lead and zinc ores.

In the operations heretofore in use, spiral classifers have been employed in the process as densiers, providing a density-regulating means in advance of the actual heavy-media separation. This heavy-media separation has been performed in conical tanks, and where large tonnages are treated by these methods a considerable amount of head room has to be provided, due to the shape of the tank. Also, in the present treatment cones, the proportion of ore to liquid in the material under treatment is relatively small, for which reason machine sizes are large in proportion to the tonnage of ore treated.

Itis an object of the present invention to provide a simple, economical and efficient heavymedia separation in which there is a relatively high proportion of solid to liquid in the material under treatment.

Another object of the invention is to provide a simple, economical and eiiicient heavy-media separation in which a relatively large tonnage of material taken for treatment is processed in a plant of limited size.

A further object of the invention is to provide selective controls of the factors of density, pulp ratio and treatment time in a heavy-media. separation.

Still another object of the invention is to provide a novel type of classifier apparatus suited for performing heavy-media separations.

Other objects reside in novel steps and treatments and novel combinations and arrangements of parts, all of which will be described in the course of the following description.

While the present invention may be practiced in a variety of ways and in a variety of apparatus, the accompanying drawings illustrate a typical treatment and typical structural embodiments for performing the treatment. In the drawings in the several views of which like parts have been designated similarly,

Figure 1 is a diagrammatic flow sheet representation of the arrangement of .equipment utilized in performing a heavy-media separation according to the present invention;

Figure 2 is a side,elevation of a classier of the Akins type, partially broken to show in section the arrangement of parts adapting it for heavy-media separations; 'Figure 3 is a plan view ofthe separation chamber of thev classier illustrated in Figure 2, seen from the approximate position of the lines 3-3 in Figure 2;

Figure 4 is an 'end elevation of the classifier shown in Figure `2, viewed from the pool-forming end of the tank;

Figure 5 is a section taken along the line 5 5, Figure 2; and

Figure 6 is a fragmentary side elevation, partially broken,.of the reciprocating rake type classier embodying features of the present invention.

The practice of the present invention will be best understood by citing a typical treatment. In this case an iron ore from Minnesota iron range and comprising a mixture of iron ore and gangue minerals was selected as the product for treatment. The heavy-media employed in the operation is ferro silicon having a speciiic gravity of 6.7 `and employed in varying degrees of density throughout a continuous operation. f

ence to the ow sheet, Figure 1. Ore' taken for treatment is delivered by a suitable conveyor 6 onto a washing screen 'I. The fine ore separated by this screening action is collected at 8 and is discharged from the circuit and passed to a separate fine ore treatment.

The oversize screened product of the separation is collected at 9 and then is passed to a heavymedia separator l0. This separator involves a novel design and operation in heavy-media separations, the details of which will be explained hereinafter. The raked product or sink concentrate is discharged at II and passed to a sink `washing screen I2. The sink concentrate product of this separation is delivered onto a conveyor `I3 and discharges as the iinal product of the treatment.

The iioat product of the heavy-media separation passes to a oat drainage and lWashing screen I5. In this operation most of the heavy medium in the overiiow from the heavy-media separator is formed as one product at I5 and iiows to a pump I9 which returns the heavy medium so separated to mix with the incoming ore as the feed to heavy-media separator I0. Such heavy medium as does not drain readily at I6 is washed oiT the iioat` product by water sprays and is collected as a light ydensity liquid at I 1.

'Ihe light density liquid collected at rI4 from the sink washing screen I2 and that collected at I1 from float drainage and washing screen I5 is moved by a pump 20 to a thickener 22 and prior -to its delivery into the thickener the liquid is passed through magnetizing blocks 2 I. The thick- The treatment will be best understood by referl circuit simplifies ener overow is passed to a water clarification thickener 32, while the sludge is moved into a primary magnetic separator 23.

The tailings of the primary separator treat-l ment constitute the feed to a secondary magnetic separator 26. The tailings 23 of this secondary separation are passed to waste or to a water re* covery treatment, while the primary concentrate 24 and the secondary concentrate 21 are conducted as the feed to a densier 23.

This latter unit which is a modied type Akins classier has been in use in heavy-media separations. The overflow product of the densiiler is delivered into the water clarification thickener 32. The densiiied product is discharged and collected at 30, and then subjected to the action of a demagnetizing coil 3|.

The product of the latter action is then mixed with the ore feed and return medium being de livered into the heavy-media separator I0. This the treatment procedure in heavy-media, separations of iron ores and the like, and this simplification isv due largely, if not entirely, to the eiliciency of the separator l0, the construction and operation of which will be described now.

Figures 2, 3, 4 and 5 illustrate a typical embodiment of the invention. In this form, the tank IIJ is normally positioned in an inclined position and has at its lower end a separation compartment 34, the details of which will be described hereinafter. A'sink concentrate discharge outlet (not shown) is located at the upper end of the tank.

A spiral conveyor mounted on a shaft 36 eX- tending through the tank from the compartment 34 to the upper end of the tank moves settled solids through a conveying and drainage zone to the sands discharge. The shaft is supported in a swivel bearing 31 at the upper end and at its lower end is connected with a lifting mechanism 38. A motor 39 drives the shaft through the provision of suitable gearing 4|). f

The swivel bearing and lifting mechanism are conventional features in the Akins classifiers' sold by Colorado Iron Works Company, and such features, per se, form no part of the present invention.

The feed compartment 34 is formed by a sloping end wall 4I, having an overflow lip 42 at its upper end, and a partition 43 which extends completely across the tank but .terminates in spaced relation to the bottom of the tank to provide a passage 44 between compartment 34 and the interior of tank I0. Preferably, this partition will in heavy-media separations. such as that shown in Figure 1, the media returned from densifler 29 and recirculated by pump I3 mixes with incoming feedbox- 45. Due to the capacity and action of the separator Il, this intermixture may contain a relatively large quantity of iron ore.

The intermixture. thus introduced, descends through the feed box and then separates, with a `light siliceous matter rising to the surface, while the heavy iron ore and some ferro-silicon descend and pass through passage 44 into the conveying 'and drainage zone. The splitter 46 distributes the matter so descending before it passes into the vconveying and drainage zone and thus provides a uniform sink concentrate load throughout the -extent of the spiral.

The material passed into the conveying and ldrainage zone is moved progressively by the spiral i until it travels out of the pool and finally reaches the sink concentrate discharge. Liquid, inclusive `of the heavy-media suspension, drains from the ore as it passes upwardly from the pool and as a consequence the ironproduct so separated requires very little subsequent treatment, and may have a moisture content of as little as 10%.

The siliceous matter rising to the surface of the body in compartment 34 is overowed across lip 42, and some Vof the heavy media passes with it. The walls 41 exert a crowding action on the siliceous matter rising to the surface, and to accommodate volume and density variations, these walls are adjustable to vary the superficial area and volume of this separation zone. In this way,

a superelevation can be created Within the lpool which further assists theseparation.

The arrangement of the separation comparti ment 34 permits the operator to see what is happening in the separation zone, and by making relatively small volumetric adjustments, operation under optimum conditions can be effectively maintained.

' same type of heavy-media separation. The tank be mounted in tank I0 for adjustment to different elevations to vary the size of passage 44.

A feed-box 45 is located in the upper portion of compartment 34 and has open ends to admit and direct feed into said compartment. A splitter member 46 is positioned beneath the feed-box and serves to distribute solids descending therefrom.

For some purposes it may be necessary to exert a crowding action on the oat material and this is provided for by adjustable partitions 41 which may be selectively positioned in one of a series of cooperative slots in partition 43 and end wall 4I.

The slots have not been shown because the scale of the drawings does not permit, but 'the several positions of adjustment are indicated by the dotted line representations of Figures 3, 4 and 5.

In the case of shutdowns, the rakes 35 can be raised by Alifting mechanism 38 which rotates shaft 36 about swivel bearing 31. When operation resumes, the blades are dropped back gradually until the shaft reaches its normal operating position, and in this way damage to the mechanism from excessive stresses is avoided.

The unit illustrated in Figure 6 employs the Ia of this form is mounted at an inclination and has a sloping end wall 50 having an overow 1ip` 5 I in its upper surface. Material settling in tank [0a is moved to an upper sink concentrate discharge (not shown) by rakes 52 which are moved in a reciprocating cycle by mechanism 53, the details of which are conventional.

The tank Illa is divided by a partition 54 into a separation zone 55 -connecting with the conveying and drainage zone through a passage 56. A

feed-box 51 adjoins partition 54 at its top for the supply of material to be treated and heavy-media to the compartment 55.- A splitter 58 divides and distributes the incoming -material before the heavier material travels through passage 56 into the conveying and drainage zone.

The action in compartment 55 is identical with that Ihereinbeiore described with reference to compartment-34 of Figure 2; After the solids enter the conveying and drainage zone they are moved by the rake mechanism 52, 53 to an upper point of discharge with heavy-media draining back into the pool. f

While. the separation can be yperformed efore from washing screen 'I and is fed into i and sink concentrate that must mechanism that might occurdue to slippage of ,the load of raked product.

If desired, a washing action may be utilized with this treatment whenever extra dilution is not undesirable. In such case the conveying and drainage zone will be provided with a wash box assembly of the type shown and claimed in Dickson application Serial No. 471,989, illed January 1l, 1943, for Classier apparatus.

From the foregoing description it will be ap parent4 that the heavy-media separation of the present invention aiords many advantages. The low head design simplies mill arrangements, and due to the pulp ratios employed, a relatively large tonnage of ore can be treated in standard sized classifiers to which the features of the present invention have been applied. Apparatus in use at present utilizes an air lift to elevate the sink concentrate and heavy medium to a drainage and 'washing screen and as noted heretofore, the percentageweight of dry concentrate in the air lift discharge is relatively small compared to the total weight of medium be elevated.

'Ihe operation of the presentinvention results in delivery of a mixture of sink concentrate and medium in which the percentage weight of sink concentrate is relatively high; The economies effected due to this fact are:

l. Elimination of an air compressor;

2. Elimination of the drainage section of the former drainage and washing screen;

3. A reduction in the size of the pump required to return heavy medium to the separating appaf ratus, from which it follows that less power is required for this work;

4, The rotation of shaft 36 and spiral conveyor 35 in the machine of Figure 2 performs a double duty of conveying sink concentrate and agitating the mass of medium to maintain a constant density of heavy' medium, whereas in apparatus-in present use separate devices, both of which require power, are required to perform these essential duties.

For this reason, a relatively simple treatment circuit of the type shown in Figure l is all that is required in attaining efcient separation. Consequently, both initial costs and operating expenses are quitenominal as compared with other types of heavy-media separations.

The invention has been described with particular reference to iron ore treatments for which it is well suited, but' it also may be utilized in the treatment of other materials. F'luorspar and lead-zinc ores are examples, although the treatment may be practiced with almost any material where the separation of gangue and mineral can Ibe made at relatively coarse sizes.

It will be noted that in both the forms shown in Figures 2 and 6, the separation and conveying and drainage zones are physically separated but have a communicating passage between their lower portions. Due to the high density pulp body in the conveying and drainage zone, suiiicient pressure is exerted on the heavy-media body to keep it confined in the separation zone.

f course, some heavy-media passes into the conveying and drainage zone with the sink product, but the agitatlve action tnepooi com- Ybined with the tumbling. impartedl to,`v the raked product in its progressive movement away from the pool, serves to release a substantial amount of the entrained heavy-media which drains back into the pool.

To facilitate this action in the conveying andv I drainage compartment, it is preferred to use a spiral conveyor of multiple ribbon construction and thereby provide separate blades 35a and 35h operating in close proximity to passage 4I. Consequently, solids entering the conveying and drainage compartment are acted on by the blades without undue delay and are progressively moved through the pool and upwardly along vthe inj clined bottom to the elevatedA discharge outlet.

While the invention has .been illustrated and described with reference to simplex type classi-` fiers, it will lbe apparent that the same relationship can be provided between the separation compartment and the conveying and drainage zone of a duplex type classifier. The accompanying drawings are intended to illustrate typical embodiments of the invention and corresponding arrangements can be incorporatedy in a variety of apparatus.

Under certain conditions it may be preferable to vary the size of the feed opening and an adjustable baille or gate may be provided for this purpose. Similarly, it may be desirable to vary the vertical dimension of the separation zone and this can be accomplished by placing slats as an adjustable Weir on the overflow lips 42 and Despite all these variations in the. structural features, the separations performed are essentially the same, and changes and modiiications may be availed of within the spirit and scope of the invention as dened in the claims.

What I claim and desire to secure by Letters Patent is:

1. Apparatus for heavy-media separations, comprising a tank having three sides and a sloping bottom, one of saidsides including'an overflow weir, the level of which is lower than the upper end of4 said sloping bottom, a partition adjacent the lower end of the tank dividing its interior hereunto appended into a relatively small separation Zoneand a relatively large conveying and drainage zone disposed in end-to-end relation, and said partition being spacedfrom the tank bottom to provide a passage between said zones, a body of heavymedia in the separation zone, a feed box in the separation zone having its intake above the Weir overflow level and ha'ving its lower end submerged in the heavy media, abody of pulp in the conveying and drainage zone exerting pressure on the'heavy-media through vsaid passage, and conveying means in the conveying and drainage zone for moving settled solids through the pulp body and upwardly along the sloping bottomA to a point of discharge at a higher elevation than said pulp body.

2. Apparatus for heavy-media separations, comprising a tank havingthree sides and a sloping bottom, one of said sides including an overilow weir, the level of which is lower than the upper end of said sloping bottom, a partition adjacent the lower end of the tank dividing its interior into a relatively smal-l separation zone and a relatively large conveying and drainage zone disposed in end-to-end relation and said partition being spaced from the tank bottom to provide a passage between said Zones, a body of heavy-media ing bottom, i flow weir, the level of which is lower than the ing bottom, one of 7 in the separation zone, a reed box in the separation zone having its intake above the i weir overflow level and having its lower end submerged in the heavy-media, a bodyl of high dens`ity pulp in the conveying and drainage zone exerting pressure on the heavy-media through said passage, and conveying means in the conveying and' drainage zone for moving settled solids through the pulp `body and upwardly along the sloping bottom to a point' of discharge at a higher elevation than said pulp'body.

3. Apparatus for heavy-media separations, comprising a tank having three sides and a slopone of said sides including an overupper end of said sloping bottom, a partition adjacent the lower rencl of the tank dividing its interior into a relatively small/separation zone and a relatively large conveying and drainage zone disposed in end-to-end relation and said partition being spaced from the tank bottom to provide a passage between said zones, a body of heavy-media in the separation zone, an openended feed-box in the separation `zone having its intake above the weir overflow level and having its lower end submerged in the heavy-media, a body of pulp in the conveying and drainage zone exerting pressure on through said passage, and conveying means in the conveying and drainage zone for moving settled solids through the pulp body and upwardly along the sloping bottom to a point of discharge at a hlgherelevation than said pulp body.

4. Apparatus for comprising a tank having said sides including an overflow` Weir, the level of which is lower than the upper end of said sloping bottom, a partition adjacent the lower end of the tank dividingits interior into a relatively small separation zone and a relatively large conveying and drainage zone disposed in end-to-end relation and said partition being spaced from the tank bottom to provide a`passage between lsaid zones, a body of heavy-.media in the separation zone, a .feed-box in the separation zone having its intake above the weir overflow level and having itslower end submerged in the heavy media, means for varying the volumetric capacity of said separation zone, a body of pulp in the conveying and drainage zone exerting pressure on the heavy-media through said passage, and conveying means in the conveying and drainage zone for moving settled` solids through the pulp body and upwardly along the sloping bottom to a` point of discharge at a higher elevation than said pulp body. l

5. Apparatus for heavy-media separations, comprising a tank having three sides and a sloping'bottom. one of said sides including an overflow' Weir, the level of which is lower than the upper end of said sloping bottom, a partition adjacent the lower end of the tank dividing its interior into a relatively small separation zone and a relatively large conveying and drainage zone disposed in end-to-end relation and said partition being spaced from the tank bottom to provide a passage'between said zones, a body of heavy-media in the separation zone, a feed-box in the separation zone having its intake above the weir overflow level and having its lower end submerged in the heavy-media, a bodyof high` density pulp in the conveying and drainage zone exi erting pressurev on the heavy-media through said passage, and a spiral conveyor in the conveying and drainage zone for. moving settled solids heavy-media separations, three sides and a slop- 8 Y through the pulp .body and upwardly along the sloping bottom to a point of discharge at a higher elevation than said pulp body.

6. Apparatus for heavy-media separations,

comprising a tank having three sidesv and a sloping bottom, one of said sides including an overow Weir, a partition adjacent the lower end of 'the tank dividing its interior into a separation zone and a conveying and drainage zone and yspaced from the tank bottom to provide a pas` feed-box to distribute solids descending therethe heavy-media through, a body of pulp in the conveying and drainage zone exerting pressure on the heavy-l media through said passage, and conveying means in the conveying and -drainage zone for moving settled solids through the pulp body and upwardly along the slopingvbottom.

7. Apparatus for heavy-media separations, comprising a tank having three sides and a sloping bottom, one of said sides including an overflow Weir, the level of which is lower than the upper end of said sloping bottom, a partition adjacent the lower end ot the tank dividing its interior into a relatively small separation zone and a relatively large conveying and drainage zone and spaced from the tank bottom to provide a passage between said zones, a body of heavys media in the separation zone, a feed-box in the separation zone having its intake above the Weir overflow level and having its lower end subvolumetric capacity of the separation* zone for exerting a crowding action on the float product in the separation zone, a body of pulp in the conveying and drainage zone exerting pressure onl the heavy-media through said passage, and con-v veying-means in the conveying and drainage zone for moving settled solids through the pulp body and upwardly along the sloping bottom to a point of discharge .at a higher elevation than said pulp body.

Q8. Apparatus yfor heavy-media separations,

kcomprising a tank having three sides and a sloping bottom, one ofv said sides including an overflow Weir, the level of which is` lower than the upper end of saidv sloping bottom, a partition adjacent the lower end of the tank dividing its interior into a relatively small separation zone and a relatively larg;J conveying and drainage zone disposed in end-to-end relation and said parti` tion being spaced from the tank bottom to proy vide a passage between said zones, a body of heavy-media in the separation zone, a bodyV of pulp in the conveying and drainage zone exerting pressure on the heavy-media through said passage, means for feeding heavy-media and ore to the separation zone, and conveying means in the conveying and drainage zone for moving settled solids through the pulp body and upwardly along the sloping bottom to a point of discharge at a higher elevation than said pulp body. v

9. Apparatus for heavy-media separations, comprising a tank having three-sidesand a sloping bottom. one of said sides including an over-` ilow Weir, the level of which is lower than the upper end of said sloping bottom,-avpartition adjacent the lower end of the tank dividing its interior into a relatively small separation zone and a relatively large conveying and drainage zone disposed in end-to-end relation and said parti tion being spaced from the tank bottom to provide a passage between said zones, a body of heavy-media in the separation zone, a body of pulp in the conveying and drainage zone exerting pressureon the heavy-media through said passage, means for feeding heavy-media and ore to the separation zone, and conveying means in the conveying and drainage zone positioned to act on solids traveling throughy the passage to move said solids progressively through the pulp b ody and upwardly along the sloping bottom to a point of discharge at a higher elevation than said pulp body.

' 10. Apparatus for heavy-media separations, comprising a tank having three sides and a sloping bottom, one of said sides including an overflow weir, the level of which is lower than the upper end of said sloping bottom, a partition adjustably mounted adjacent the lowerend of the tank to divide its interior into a relatively small separation zone and a relatively large conveying and drainage zone disposed inend-to-end relation and movable'to differently spaced positions relative to the tank bottom to provide a passage between said zones, a body of heavy-media in the.

separation zone, a feed-box in 'the separation zone having a submerged outlet in the heavy-media body, a -body of pulp in the conveying and drainage zone exerting pressure on the heavymedia through said passage, and conveying means in the conveying and drainage zone for moving settled solids through the pulp body and upwardly along the sloping bottom to apoint of discharge at a higher elevation than said pulp body.

11. The heavy .media separation process which comprises maintaining a pool of relatively large volume and a pool of'relatively small volume in end. to end' relation with a restricted flow path from the bottom of the small volume pool into the lower portion of the other pool, maintaining a -l common levely for said pools by the continuous overflow of float material from the surface of the small volume pool, maintaining abody of heavy media in the small volume pool between the restricted flow path and the surface of the pool. continuously introducing material to be separated into said heavy media body, moving the sink product descending through the restricted zone into said larger volume pool upwardly along an inclined course through and out of said pool to a point of discharge above the pool, and agitating the solids in the larger volume pool to maintain in suspension a substantial portion of the sink product content to thereby create a high density head directed against the restricted zone to restrict settling of float material into said zone.

12. The heavy media separation process which comprises maintaining a pool of relatively large volume and a pool of relatively small volume in end to end relation witha restricted ow path from the bottom of the small volume pool into the lower portion of the other pool,v maintaining' a common level for said pools by the continuous overflow of float material from the surface of the small volume pool, maintaining a body of heavy media in the small volume pool between therestricted ow path and the surface of the pool, continuously introducing material to be separated into said heavy media body, moving the sink product descending through the restricted zone into said larger volume pool upwardly along an inclined course through and out of said pool to a point of discharge above the pool, agitating the solids in the larger volume pool to maintain in suspension a substantial portion of the sink product content to thereby create a high density head directed against the restricted zone to restrict settling of oat material into saidzone, separating entrained media from the sink pjrduct moving out of the larger volumelpool along the inclined course, and returning the separated media tothe high density body `in said larger volume pool.

13. The heavy media separation process Vwhich overflow of float material from the surface of the small volume pool, maintaining a body of heavy media in the small volume pool between the restricted flow path and the surface of the pool. continuously introducing material to be separated into said heavy media body.' moving the sink product descending through the restricted zone into said larger volume pool upwardly along an inclined course throughand out of said pool to a point of discharge above the pool, agitating the solids in the larger volume pool to maintain in suspension a substantial portion of the sink product content to thereby create ahigh density head directed against the restricted zone to restrict settling of float material into said zone, and varying the effective volume of the smaller volume pool against which the high density head is directed. v

14. The heavy media separation process which comprises maintaining a pool of relatively large volume and a pool of relatively small volume in end to end relation with a restricted ow path fromA the bottom of the small volume pool into the lower portion of the other pool, maintaining a common level for said pools by the continuous overflow of float material from the surface of the small volume pool, maintaining a. body of heavy media in the small volume,p6ol between the re stricted flow path and the surface of the pool, continuously introducing material to be separated into said heavy media body, moving the sink product descending through the restricted zone into said larger volume pool upwardly along an inclined course through and out of said pool to a point of discharge above the pool, agitating .the solids in the larger volume pool to maintain in suspension a substantialportion of the sinkproduct content to thereby create a high density head directed against the restricted zone to restrict settling of oat material into said zone, collecting entrained media passing with the sink product into the larger volume pool from the smaller volume pool, and-inducing a return of a portion of said media to the smaller volume pool under the impelling influence of the high density head.

15. The heavy media separation process which comprises maintaining a pool of relatively large volume and a pool of relatively small volume in end to end relation with a restrictediow path from the bottom of the small volume pool into the lower portion of the other pool, maintaining a common level for said pools by the continuous overflow of float material from the Vsurface of the small volume pool, maintaining a body of ferro-silicon in the small volume pool between the restricted ow path and the surface of the pool, 'continuously introducing material to be l separated into said ferro-silicon body, moving the REFERENCES CITED The following references are of record in the ille o f this patent:

UNITED STATES PATENTS Number Name Date 1,780,830 Y y Lessing Nov. 4, 1930 2,328,428 DeKoning Aug. 31, 1943 Number Number 20 '791,132

Name v Date Foulke Mar. 21, 1939 DeVooys Mar. 8, 1938 Hirst -'May 18, 1943 Rakowsky June 4, 1940 Zeb Jan. 14, 1930 Vogel July'30, 1940 Reinick Aug'. 25, '1936 Conklin Jan. 7, 1919 Dekker Dec. 3, 1918 DeVooys i-- Dec. 31, 1935 Moxham Feb. 18, 1919 Blomeld Jan. 21, 1919 Lanaux Sept. 15, 1891 Y Daman Feb. 23, 1937 Felslng June 20, 1911 FOREIGN PATENTS Country Date France Sept. 23, 1935 Great Britain Feb. 23, 1933 

